Apparatus and process for making sheet glass



' June 29 1926.`

v APPARTUS AND -PROCESS FOR MAKING SHEET 'GLASSv lFiled Qct. 7. 1924 2 She@@f-SheetV 1 e ratus and Patented June '29, 1926..

rREDnnIcx GELSTHARP, on Tiananmen, PENNSYLVANIA.

ABSIGNOR T PITTSBURGH -PLATE GLASS CGMPNY, .A CORPORATION OF PENNSYLVANA.

APPARATUS PROCESS FOR MAKING SHEET t'rLASS.y

Application led October 7, 1924. Serial No. 742,181.

The invention relates to'an apparatus and .process for making sheet glass continuously from a tank. It has for its principal objects the provision of an improved appaprocess. wherein the Contact of the molten glass with the clay work at the end` of the tank is reduced to a minimum, thus reducing the contamination of the glass tending to cause strin and ream to l0' a minumum.; and wherein t e rolling and the visibility of such bubbles in product is made as slight as possible, a round or slightly elongated-bubble being much less noticeable than one which is stretchedvto a length lseveral times that of the'original onef the invention are illustrated inthe accompanying drawings wherein:

sizing action is'reduced, so that -F1gure 1"i s alongitudinal vertical sec-f] tion through the apparatus. Fig. 2 is/a transverse sectionfon the line II`II of Fig. 41. Fig. '3 is a transverse section on the line III-III of Fig. l.4 And Fig. 4 is a vertical section -through a modification.-

Briefly stated, the )recess consists inflowingothe glassvlateral y in a stream over a dam or lip or through aI slot or opening in I' '30 the side wall of the melting tank, receiving the glass upon a spreading table, where it piles up and spreads out in a layer of much greater widththan that of the outlet slot, and then passing the glass beneath a sizing roll disposed above the table, intermediate its ends, traction force being applied to the glass in advance of the roll whereby it is continuously drawn over the surface of thetable and beneath the sizing roll. This `continuously and progressively removes the chilled bottom surface, which is formed as the Kfmolten glass comes in contact y with the water cooled table. This chilled skin transmits the traction over the 'l surface ofthe table from the point where the :hot glassv rst touches it, so that at no time is there stagnant glass remaining on the' table. This prevents any tendency for devitrication to take lace. skin i'n a great measure-insulates the molten glass above it and the progress of the mass of glass is such that the chilled outside sur faoesh-re removed automatically in the formation of the sheet. It it were not for this action, it would not be possible to pour `elongation of any bubbles in the glass,

lengthening. of any bubbles in the glass incident to thev the finished' How; thus glass due to freedom from contamination by 4 Certain embodiments of require a clay'transporting surface The spreading action of thesheet vadjusted by regulatin The chilled metal on a stationary table in front of a pair of rolls/and continue to form a sheet from it. f

This procedure also tends to prevent an which the sizing might otherwise cause, since the lateral spreading of the glass on the table, preliminary to sizing, tends to y widen them laterally, and thus tends tov counteract the'lengthening tendency due to the sizing. l

By the uselof a stationary spreading table, itis possible to obtain the minimum length of clay lip over which the molten glass must preserving. the quality of the methods which have been used two to method.' may be the .feed of the molten glass tothe tabe in'relation to the speed with which the glass sheet is withdrawn from. the forward side of the sizing roll( and by varying the tempera-ture of the glass before or after it passes onto the table or both.

Referring to the drawings, listhe outlet end ot' a melting tank, preferably of the wellkncwn regenerator type', havingan outlet 2 below the level of the glassin t'he tank, and controlled by means of the gate 3, supported upon-suitable means 4 for adjusting its vertical position. Backl of this regulating gate is a water cooled cut otl gate 5, also mounted for vertical movement upon/the chains 6, and adapted to entirely cut oil the supply of glass 1n case of emergencies, or-in case it becomes necessary to shut down the tank for any considerable. time for replacements or repairs. Back of the gate 5 is a shade 7 of clay supported upon the chains 8, whichmay'be lowered to the surface of the glass when the gate 5 is lowered, so that the glass back'of the gate will not be unduly chilled by the water' cooled gate during the shut down. The Water cooled gate is provided with inlet and outlet pipes, as is common in apparatus of `this kind, so that a cooling circulation of water-may be maintained.

Forward of the outlet 2, in position to receive the glass, is the table 9, which table is preferably made hollow and basa. polished surface. Waterjs circulated through the' 9 clay.. Other three times longer than by 'this los' 2, arredare table in order to produce a 'chilled skin on the bot-tom surface of the glass. This table is much Wider than the out-let 2 (preferably from six to twelve times as Wide), so that a sheetmay be formed which is several times as Wide as the outlet, the purposeigbe ing to cause the glass to spread laterally upon the table, preliminary to sizing by means of the roll 1.1. This roll is coole-d by cir culating Water therethrough, and is driven in the direction indicated bythe arrow from the motor 12, (F ig. 2), through the intermediary of the reduction gearing in the casing 13 and the tumbler vshaft let. The shaft of this roll carries the spur gear 15. The table is referred to in the claims Yas stationary in the sense that its upper surface is stationary with respect to the glass dui-ing the operation, as opposed to the type of table heretofore contemplated which is niade in the 'form ot a forwardly moving endless carrier i which moves along with the glass.

Forward of the sizing roll 11, are a pair of traction rolls 16 and 17, also Water cooled, aiid carrying spur gears 18 and 19. A pin-I ion 20, interposed ,between the gears 15 and 18 serves to drive the gears 1S and 19 from the gear 15.

At'ter passing the traction rolls 16 and 17, the glass sheet is conducted through the leer 21, which maybe of any approved torni, but is preferably heated hy gas burners, and is provided with a series ot' driven rollers). upon which the continuous glass sheet 23de supported and carried forwardly. Intermediate the traction rollers and the leer is an apron 24, also providedl with driven rollers for supporting the. glass sheet. This -apron is surrounded by a clay wall to prevent the glass cooling too rapidly at this point, including a portable cover 2G and a bottom 27 carried upon a. truck 2S, thus pro riding for the removal ot' the apron to give access to the end vot ythe leer and the rolling mechanism in case replacements or repairs are required.` The space between the tank end and the sizing roll llis also provided ivith a removablecover l() to reduce the rcdiietion o'i'j heat at thisl point.y (las burners are employed atthe openingsl() 'for giving' the desired temperature, and a pair ot transversely extending burners 3l and 32 are provided toi securing the proper i'ieinperature vin the glass upon the table i). ln some cases air instead of gas, maybe supplied through the pipe 33 as a cooling medium to control the back [low ot the glass at 40. The burners 33 are directed on the side edges ot the body of glass on the table and assist in regulating the spreading ot' the glass laterally and also prevent too rapid cooling of the edges and the vformation ot small cracks at the edges of the finished sheet, which cracks tend to cause breakage.

The leerrolls 22 are provided at their ends is received upon the table 9,and spreads out laterally to approximately the Width of the finished sheet before engaging the sizing roll 11. The glass also tends to tloivto the rear, as indicated at 40 (Fig. 1), the extent being regulated by the application lot heat hy the gas burner 32, or it may be cooled. by air throughv the vpipe 32.

The sizing roll` reduces the sheet to uniform thickness, and' feeds it forward to the traction rolls 18- and 19. The contact ofthe glass With the cooled table and cooled sizingroll produces a solidified skin on the upper and lower surfaces ot' the sheet, so that there is little or no stretching or thinning of thel glass between the sizing'roll and the-traction rolls.

The traction rolls feed the glass forward intov the leer Whe-re the glass attains a. seinewhat higher temperature, preliininary'to annealing. The apron rolls 25 in conjunction with the leer rolls Q2 would exert sufficient pull on the sheet to carry it into the leertroni the sizing roll 1l, but because of `the necessary sottening ot the skin of the glass in 'the entrance portion of the leer in order to secure proper annealing, the traction rolls .18 and 19 are necessary to prevent the glass troni stretching either on the apron or in the` hot portion ot the leer. The traction rolls toed the sheet ahead at a rate which isthe saine as the peripheral speed of the rolls Q5 and 22, so that there is vno stretching ot the* sheet, when the sheet is reheateth.preliminary to annealing.

From the hot end of' the leer on, the. glass. is very 'gradually cooled through the critical annealing range` and then down to apoint where-it may be cnt The glass thus produced, is flat'and has a suii'ace `which requires a minimum amount of grinding preliminary to polishing.

Since the glass is spread laterally preliminary to sizing, any tendency of the sizing;l to lengthen bubbles in the glass is neu-` tralized. so that such biibbles'retain their spherical .forni instead ot being rolled or drawn into strings or lines 'which constitute much more noticeable and objectionable de" tects than the spherical bubbles. The lat et' n ot the glass also tends to t, i a as stones or dirt, to the side edges lf; and any surface iinpuri=- -lli .and handled -at the outlet end offtlie leer.`

l the glass at which points they impair t e' value of the sheet produced to agminimum extent, and further,'the glass at the surface Where the greater portion of the bubbles collect has come chilledand stilenbefore the sizin of the glass, so thattlie action of the roll does not flatten or lengthen them as would `be thccase il the glass were' hotter and softer. yThe lower surface of thev sheet formed is relatively' smooth due to the fact that it is drawn over the polished surface of the table, lso that the grinding of this surface is reduced to a minimum. It also happens that the fluid surface glass (which ovvs to the sides ot the sheet carrying the bubbles which lrislJ to the surface) after reaching such side edges flows around the edges of the lower side of the sheet Where it receives a heavy chill before reaching the sizing roll. The vbubbles are thus'contined for the most part to the lower skin of glass and are consequently eliminatediwhen such lower skin is removed in the grinding operlation` rthe contamination ot the glass by the clay Work of the outlet is reduced to a minimum, because of the relatively narrow Width of the slot 2,

as compared with the ,Width of the finished sheet, the outlet 2. .giving less clay area 1n contact with the glass than a Wider slot ot less depth. The

reduced clay contact also yreduces the .bubble formation. Other advantages of the con,- struetion incident to its simplicity and ease ot" control-ivill he apparent to those skilled in the art. l

Fig. 4 illustrates a modification in which the table 38 is inclined to the horizontal and has at its rear edge the water cooled Hangev ln other respects, this construction folvlows that of Figs. l to and has 'the same method of operation.

il hat l claim is; l.. In apparatus for'the manufact-Ure of vsheet the combination with a tank or receptacle provided with an outlet, so ,as

'to permit the discharge therethrough of molten glass under the head pressure ot the tank, n stationary spreading table in position todreceive the molten glass from said outlet ot a width much greater than that of said outlet. a sizing roll over the table intermediate the ends thereof, a pair o'f traction rolls in advance ot the sizing roll for engaging the upper and lower sides of the sheet and pulling it over thesurface ot the table and beneath the sizing roll, and a leer in advance ot said traction rolls provided with `means for carrying the glass therethrough.

2. In apparatus for the manufacture of sheet glassi the combination with a tank or receptacle provided with an outlet, so as to permit the discharge therethrough of molten glass under the head pressure of an opportunity to be` f or receptacle the tank? a stationary-spreading table in position to receive the molten glass 'from said outlet of a width much greater than that of `said outlet, a sizingroll over" the table intermediate the ends thereof, afl-Elin' g of traction rolls in advance of the sizihg roll for engaging'the upper and lower sides of the sheet and pulling it over the surface of the table and beneath the sizing roll, means for cooling said tahleand the sizing roll, and a leer in advance of said traction rolls provided with means for carrying the glassIsheet therethrough.

3. sheet glass, the combination with a tank or receptacle permit the discharge therethrough of molten glass under the' head pressure of the tank, a stationary spreading table in position to receive the molten glass from'said outlet of a width much greater than that of said outlet, a sizing roll over the table intermediate the ends thereof, a pairf of traction rolls in advance of the sizing roll for engaging the upper and lower sides of the sheet and pull-` ing it over the surface of the table and beneath the sizing roll, means for cooling said table and the sizing roll, and said traction rolls, and a leer in the glass therethrough.

provided' with an outlet, so as to In apparatus for the manufacture of.:V

sheet glass, the combination with a tank provided with an outlet, so as t0 permit the discharge therethrough of molten glass under the head pressure ot"i the tank, a stationary spreading;r table A,in positionto receive the molten glass from said Aoutlet of a width much greater than that of said outlet, a sizing roll over thc table intermediate the ends thereof. a' pairof traction rolls in advance of'fthe'sizing` loo roll for 'engaging the upper and lower sides c ot' the sheet and pulling it overthe surface.'

of the tahle,and beneath'the sizing roll,`

llO

means for applying heat to the. glass upon the table, a d ay leer in advance ofthesaid traction rollis rying the glass therethrouglf, t

5. Tn apparatus -for the manuiiicture of sheet glass, the'combin-ation with a tank or receptacle provided -with an outlet, so

as to permit the.disolmrgo therethrough of molten glass under thehead pressure of.' the tank,4 a stationary spreading table in position to receive the molten glass from said outlet ot' ay width much greater than that of said outlet, a sizing roll `rover the table intermediate the ends thereoi a pair of traction rolls in advance of the sizing roll for engaging the upper and lower sides of the sheet and ulling it over theurface of the table anclp beneath the sizing roll, means for applying heat to the edges of the glass upon the table, and a leer in adrprovided with meansv forear- 30 tinuously annealing thesheet.

. 40 ously over thetable and Vance of said traction rolls forl carrying the glass therethrough. Y 6. A process of making sheet glass, which consists in flowing it laterally from a re- 5 ceptacle' in a shallow stream of less width than that of the sheet to be formed, receiving it upon. a stationary spreading table, causing the' glass `te-spread `laterally to approximately the Width ofthessheet to be produced, applying rolling pressure `to the upper 'side of` vthe sheet in opposition to the table to reduce it to uniform thickness, applying tractive force to the upper and lower surfaces ofthe sheetV in advance of the table to advance the-sheet'continuously ceptacle in a shallow strenrreqfless Width 'than that of the sheet to be foriied,k refy ceiving it -upon a stationary spreading table,

cooling the table, applying rolling pres.

sure to the upper side `of Vthe sheet in opposition to the table to reduce it to,uniformn thickness, applyingtractive force to the upper and lower surfaces of the sheet in advance of the table to advance the sheet continuously over the table and then con-` 8. A process-of making sheet glass", which consists in flowing it laterally from a,`freceptacle in a shallow streamupon la ystationary table, applying rolling pressure to the upperl side of -the sheet in opposition to the table to reduce it to uniforni'thickiiessapplying*tractive force to the iipper and lower surfaces of the sheet in advz'xnceA of the table to advancev the sheet continuthen continuously annealing the sheet.

9. A process of making sheet glass, which consists in flowing it' laterally 'from a re ceptacle in a shallow stream of less width than that of the sheet to he formed, re-

ceiving it. upon a stationary spreading table,

@causing the glass/to spread laterally lto approximately the. width of the sheet to consists in flowing it laterally from a receptacle in a shallow stream of less width than that of the sheet to he formed, re- '.ceivi'ng it upon a stationary spreading table, causing the glass to spread laterally to [approximately the width of the sheet to be produced, applying heat to the glass upon the table to regulate its temperature and spreading action, applying rolling pressure to the upper side of the sheet in opposition to the table tol, reduce it to luniform thickness, applying tractive force to'tlie upper and lower surfaces of the sheet in advance of the table to advance the sheet continuously over the table and then convvitinuouslynnealing the, sheet.... V Y l1. A processv of making sheet glass, which consists in flowing it laterally from a vreceptacle in a shallow streamof less /lwidth than that of the sheet to be formed,

receiving it upon a stationary spreading table', ncausingthe glass to spread laterally' to approximately the width of the sheet to .be produced, applying heat to ythe glass upon the table at the side edges thereof, to Iref gfulate itst temperature and spreading action, applying rolling pressure to the .upper side of the sheet in Vopposition to th applying tractire force to the upper and y lower surfaces of the sheet in advance of the table to advance the sheet continuously over the table and then continuously annealing the sheet. l

In testimony whereof, I have hereunto subscribed my name this 23rd day Sept., 1924.

lFREDERICK GELSTHARP. F

table ltoI reduce `it to uniform thickness, 

